Semiconductor reaction chamber showerhead

ABSTRACT

A showerhead including a body having an opening, a first plate positioned within the opening and having a plurality of slots, a second plate positioned within the opening and having a plurality of slots, and wherein each of the first plate plurality of slots are concentrically aligned with the second plate plurality of slots.

FIELD OF THE DISCLOSURE

This disclosure relates generally to semiconductor processing, and more particularly to an apparatus and method for providing a processing gas to a substrate or wafer in a reaction chamber.

BACKGROUND

Semiconductor fabrication processes are typically conducted with the substrates supported within a chamber under controlled conditions. For many purposes, semiconductor substrates (e.g., wafers) are heated inside the process chamber. For example, substrates can be heated by direct physical contact with an internally heated wafer holder or “chuck.” “Susceptors” are wafer supports used in systems where the wafer and susceptors absorb heat.

Some of the important controlled conditions for processing include, but are not limited to, pressure of the chamber, fluid flow rate into the chamber, temperature of the reaction chamber, temperature of the fluid flowing into the reaction chamber, and wafer position on the susceptor during wafer loading.

Heating within the reaction chamber can occur in a number of ways, including lamp banks or arrays positioned above the substrate surface for directly heating the susceptor or susceptor heaters/pedestal heaters positioned below the susceptor. Traditionally, the pedestal style heater extends into the chamber through a bottom wall and the susceptor is mounted on a top surface of the heater. The heater may include a resistive heating element enclosed within the heater to provide conductive heat and increase the susceptor temperature.

Consistent processing and consistent results generally require careful control and metering of processing gases in the system. One of the last resorts for controlling the processing gas is at the showerhead where the processing gas then contacts the wafer in the reaction chamber. Further, obtaining optimal flow rates and uniformity may be difficult at times due to showerhead holes becoming clogged or parasitic precursor reactions occurring within the showerhead.

SUMMARY

Various aspects and implementations are disclosed herein that relate to reaction chamber showerhead designs and methods of providing a processing gas to a wafer. In one aspect, a showerhead includes a body having an opening, a first plate positioned within the opening and having a plurality of slots, a second plate positioned within the opening and having a plurality of slots, and wherein each of the first plate plurality of slots are concentrically aligned with the second plate plurality of slots.

In one implementation, the first plate slots may extend towards the second plate slots. The first plate slots may extend to a bottom surface of the second plate slots. The first and second plate slots may be oriented in a plurality of rings, wherein adjacent rings are offset with respect to one another. The first and second plate plurality of slots may be oriented in a plurality of rings, wherein every other ring is in alignment. A gap may be formed between each of the plurality of first slots and each of the plurality of second slots, and wherein the gap varies between 0.575 mm and 0.800 mm. A gap may be formed within each of the plurality of first slots, and wherein the gap varies between 0.636 mm and 1.100 mm.

In another implementation, a first gas flow cavity may be formed between the body and the first plate and a second gas flow cavity may be formed between the first plate and the second plate. The first gas flow cavity may convey a first gas and wherein the second gas flow cavity may convey a second gas. The first gas cavity may further include a purge channel separate from a first gas flow inlet. The purge channel may be positioned at a perimeter of the first cavity. The purge channel may provide additional purge gas flow during a purging operation. The purge channel may be operatively connected to an exhaust. The purge channel may remove the first gas during a purging operation. The second gas cavity may further include a purge channel separate from the second gas flow inlet and wherein the purge channel may provide a gas flow or a vacuum.

In yet another implementation, a plurality of apertures may extend from a top surface to a bottom surface of the first plate and are separate from the first plate plurality of slots. The plurality of apertures may be in fluid communication with a gas channel separate from a second gas channel in fluid communication with the plurality of first plate slots. The plurality of slots may be generally arcuate in shape. The plurality of slots may extend less than 50 percent of a circular distance of the showerhead body. A gas in the first plate slots may not contact a gas in the second plate slots until both of the gasses have traveled completely through the slots.

In another aspect, a semiconductor tool includes a reaction chamber defining a processing area, a workpiece support within the reaction chamber, a showerhead for distributing at least one processing gas within the processing area, and a processing valve manifold in fluid communication with the showerhead to control the at least one processing gas flow into the showerhead, wherein the showerhead further includes a first plurality of arcuate slots and a second plurality of arcuate slots, each of the plurality of arcuate slots having a common exit plane above a workpiece support and the first plurality of arcuate slots being concentrically aligned with the second plurality of arcuate slots.

In an implementation, the at least one process gas flows radially outward after leaving the first and second plurality of arcuate slots. Each ring of the plurality of first and second arcuate slots may be alternatively offset from adjacent rings of first and second arcuate slots. The semiconductor tool may include a vacuum port in fluid communication with the first plurality of arcuate slots and another vacuum port in fluid communication with the second plurality of arcuate slots. The semiconductor tool may further include a purge port in fluid communication with the first plurality of arcuate slots and another purge port in fluid communication with the second plurality of arcuate slots. The purge ports may be positioned radially outward of the plurality of first and second arcuate slots.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a reaction chamber with a susceptor in the wafer loading position.

FIG. 2 illustrates a top perspective view of a base member of the showerhead.

FIG. 3 illustrates a bottom perspective view of the base member of the showerhead.

FIG. 4 illustrates a top perspective view of a middle plate member of the showerhead.

FIG. 5 illustrates a bottom perspective view of the middle plate member of the showerhead.

FIG. 6 illustrates a top perspective view of an upper plate member of the showerhead.

FIG. 7 illustrates a bottom perspective view of the upper plate member of the showerhead.

FIG. 8 illustrates an enlarged view of the cross-sectional view seen in FIG. 1.

FIG. 9 illustrates a further enlarged view of the cross-sectional view seen in FIG. 8 and labeled as FIG. 9.

FIG. 10 illustrates an enlarged view of the section labeled FIG. 10 in FIG. 9.

FIG. 11 illustrates a partial bottom view of the showerhead assembly.

FIG. 12 illustrates an enlarged view of the section labeled FIG. 12 in FIG. 11.

FIG. 13 illustrates an enlarged view of a cross-sectional view of a showerhead having a plurality of ports positioned near a periphery of the showerhead.

FIG. 14 illustrates an enlarged view of a cross-sectional view of a showerhead having a plurality of ports positioned near a periphery of the showerhead and a connection between the plurality of ports and a vacuum exhaust line.

DETAILED DESCRIPTION

The present aspects and implementations may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of hardware or software components configured to perform the specified functions and achieve the various results. For example, the present aspects may employ various sensors, detectors, flow control devices, heaters, and the like, which may carry out a variety of functions. In addition, the present aspects and implementations may be practiced in conjunction with any number of processing methods, and the apparatus and systems described may employ any number of processing methods, and the apparatus and systems described are merely examples of applications of the invention.

FIG. 1 illustrates a reaction chamber 20 having an upper chamber 22 and a lower chamber 24. Upper chamber 22 includes a showerhead 26, while lower chamber 24 generally includes a susceptor assembly 28 as may be commonly known in the art which is moveable in the direction associated with arrows 30 to receive wafers (not shown) for loading, unloading, and processing. While the present disclosure illustrates and describes showerhead 26 in a split chamber with upper and lower sections, it is within the spirit and scope of the present disclosure to incorporate showerhead 26 in a non-split chamber reactor.

Showerhead 26 includes an upper plate 32, a middle plate 34, and a base plate 36. Upper plate 32 includes a plurality of cooling fins 38 extending vertically therefrom and a raised central portion 40 having a plurality of upper plate second gas holes 42 which may be oriented at an angle. In one implementation, the plurality of upper plate second gas holes 42 may be at least three gas holes, while in another implementation there may be six or more gas holes, although any suitable number of gas holes may be incorporated. Further, an upper plate first gas hole 44 may extend vertically through the raised central portion 40 and into a first gas cavity 46 defined by and positioned between the upper plate 32 and the middle plate 34. Similarly, upper plate second gas holes 42 extend through conduits 48 in the upper plate 32 and specifically channels 50 in conduits 48 to reach a second gas cavity 52 defined by and positioned between the middle plate 34 and the base plate 36. The channels 50 may also extend through middle plate 34 before entering second gas cavity 52.

A gas control valve assembly 54 may be positioned on showerhead 26 and particularly on raised central portion 40 with an inner o-ring 56 and an outer o-ring 58 preventing comingling of the gases during delivery and also preventing the gases from leaking at the intersection between the gas control valve assembly 54 and the raised central portion 40. Gas control valve assembly 54 also includes a valve assembly first gas hole 60 and a plurality of valve assembly second gas holes 62. As can be seen in FIG. 1, any suitable number of valve assembly second gas holes 62 may be utilized, however a similar number of channels 50 may be required to transport the gas beyond the first gas cavity 46 and into the second gas cavity 52. Similarly, an o-ring 64 is used to separate and seal the area between upper plate 32 and middle plate 34, while an o-ring 66 is used to separate and seal the area between middle plate 34 and base plate 36. In a still similar fashion, o-rings 68 are exemplary of each o-ring which is located where conduits 48 meet a top surface of showerhead middle plate 34 to both prevent the second gas from leaking into the first cavity and preventing the first gas from entering channels 50. Finally, as will be discussed in greater detail below, an exhaust channel 72 is formed in base plate 36 and may be fully enclosed by the base plate 36 or partially formed by the base plate 36. Exhaust channel 72 is in fluid communication with a processing area 74 through exhaust gap 76. While the present disclosure and Figures illustrate conduits 48 extending from upper showerhead plate 32, it is within the spirit and scope of the present disclosure to rearrange the orientation of the conduits so that the conduits extend vertically upwards from middle plate 34 and contact a bottom surface of upper plate 32, where appropriate sealing mechanisms, such as o-rings, may be located.

FIGS. 2 and 3 illustrate a top and bottom perspective views, respectively, of base plate 36. Base plate 36 includes a top side 78 and a bottom side 80, with top side 78 having an opening 82 for receiving the upper and middle plates 32 and 34 therein. A sealing surface 84 is positioned radially outward of slots 86, both of which are positioned within opening 82. As can be seen in both FIGS. 2 and 3, slots 86 may be generally arcuate in shape and progressively smaller radial dimensions as the slots 86 move radially inward. In another implementation, slots 86 are offset from one another such that slots 88 on the most outward ring are offset from adjacent slots 90 on the second most outward ring. This trend or orientation may continue radially inward such that adjacent rings of slots 86 are offset from one another, but every other ring of slots 90 are parallel with one another and have slightly smaller radial dimensions due to the decrease in radius of base plate 36 of each inward slot. For example, the inward most slot 90 may be shaped more like a circle instead of a slot, or the inward most slot 90 may not extend to the complete center of base plate 36 in other implementations.

As discussed above, base plate 36 also includes at least a portion of exhaust channel 72 and a portion of exhaust gap 76 is formed by the channel 72 edge. A sidewall 92 includes an exhaust port 94 with mounting holes 96 for securing a vacuum or exhaust apparatus to remove unused precursor and carrier gasses from the chamber and the exhaust channel.

Referring now to FIGS. 4 and 5, where middle plate 34 is shown in greater detail. Middle plate 34 also includes a top side 98 and a bottom side 100. A plurality of slots 102 are similar to slots 86 in base plate 36 in that slots 102 are generally arcuate in shape with decreasing radial dimensions as the various rows of slots change from radially outside to radially inside. Further, slots 102 are also positioned similar to slots 86 in that each adjacent slot rows are offset from one another, while every other slot row may be parallel or aligned with one another, having only slightly smaller radial dimensions due to the smaller radius of the plate from outside to inside. Further, slots 102 may also include smaller and smaller slots to the extent that the inner most slot 102 may be generally circular in shape. Regardless of the position, slots 102 and 86 do not extend for more than 50 percent or 180 degrees around the showerhead and may extend for only 90 degrees or less in additional embodiments.

FIG. 4 also illustrates channels 50 extending from top side 98 through to bottom side 100 and into second gas cavity 52 formed between a plurality of protrusions 104 on bottom side 100. Channels 50 may be surrounded by a recessed o-ring surface 110 arranged to receive o-ring 68 for example. In one implementation, each corresponding channel 50 and conduit 48 include their own respective o-ring to ensure that the first and second gases do not see or interact with each other until desired.

FIG. 5 more clearly illustrates protrusions 104 extending from bottom side 100 of middle plate 34 long enough to fit within slots 86 of base plate 36. Specifically, when a sealing surface 106 includes an o-ring cavity 107 and the surface contacts sealing surface 84 of base plate 36, protrusions 104 are dimensioned to extend through slots 86 of base plate 36. Even further, protrusions 104 preferably extend through slots 86 such that a bottom surface 108 of protrusions 104 are flush or even with a bottom surface of slots 86 extending through base plate 36. Accordingly, the protrusions 104 and slots 102 therein terminate co-planar with slots 86 of base plate 36 such that gas flowing from slots 102 and 86 are unable to comingle until they leave the showerhead assembly at the same distance from the wafer or work piece (not shown).

Once assembled, the area surrounding each of protrusions 104 and defined by a top surface of lower plate 36 assists to define second gas cavity 52. Specifically, the second gas can flow through the upper plate second gas holes 42 in the upper plate and into channels 50 before reaching second gas cavity 52. Second gas cavity 52 then permits the second gas to flow between an area defined by an outer surface 112 of protrusions 104 and an inner surface of slots 86 due to the complimentary shape, design, and orientation of slots 86 and protrusions 104. Further, the first gas flows through slots 102, and therefore protrusions 104, until reaching bottom surface 108 of protrusions 104. Accordingly, the first and second gases can meet just below showerhead base plate 36 bottom side 80.

Referring now to FIGS. 6 and 7, upper plate 32 is shown in both a top perspective view and a bottom perspective view, respectively. Upper plate 32 includes a top side 113 and a bottom side 114. As previously noted, a plurality of cooling fins 38 may be disposed throughout top side 113 to better control heating and gas flow rates to prevent gases from decomposing within the showerhead. Raised central portion 40 also includes an o-ring cavity 118 for receiving o-ring 58, while an o-ring cavity 120 is used to secure o-ring 56 when the gas control valve 54 is positioned on raised central portion 40.

Bottom side 114 of upper plate 32 includes conduits 48 with channels 50 as discussed above. The conduits 48 extend from a gas cavity surface 122 which assists in providing a partial barrier of gas cavity 46. Specifically, gas cavity surface 122 forms the top and side walls for gas cavity 46 and receives a first gas flow from upper plate first gas hole 44. Further, conduits 48 also act as a boundary for gas cavity 46 since they are sealed off from the cavity and convey a second gas through channels 50. Bottom side 114 also includes a sealing surface 124 having an o-ring cavity 126 formed therein. When assembled, sealing surface 124 contacts top side 98 of middle plate 34 and o-ring 64 is positioned within o-ring cavity 126 to seal the gas cavity 46 from the second gas cavity 52. While the present disclosure and illustrations provide one example of showerhead 26, a person of ordinary skill in the art will immediately recognize that a number of modifications may be made without departing from the spirit and scope of the present disclosure. For example and without limitation, the showerhead shape may be other than round, may include straight upper plate second holes 42 instead of angled holes and the size of the various holes, channels, and fins may be modified to fit the reactor application. Process gases can enter either volume as shown or even from outer perimeter feed tubes and/or purge channels as will be discussed in greater detail below.

Referring now to FIG. 8, which is an enlarged view of a portion of assembled showerhead 26 within reaction chamber 20, gas cavity 46 is formed in part by gas cavity surface 122 of bottom side 116 of upper plate 32, conduits 48, and top side 98 of middle plate 34. Gas cavity surface 122 is shown generally angled from upward from a radially outward position to a radially inward position, while top side 98 of middle plate 34 is shown as generally flat. In another implementation, gas cavity surface 122 may be generally flat and top side 98 may be angled in either direction, still further, both top surface 98 and gas cavity surface 122 may both be flat or tapered in opposite directions as may be appropriate for individual applications.

In a similar fashion, second gas cavity 52 is generally defined by bottom side 100 of middle plate 34, protrusion outer surfaces 112, and top side 78 of base plate 36. As shown, bottom side 100 of middle plate 34 may be generally flat, with top side 78 being angled downward from a radially outward position to a radially inward position. In another implementation, top side 78 may be flat, while bottom side 100 may be angled. In still another implementation, both top side 78 and bottom side 100 may both be flat or both be angled in the same or different directions without departing from the spirit and scope of the disclosure. The shape, size, and thickness of each gas cavity 46 and 52 may be angled or dimensioned to provide better flow characteristics as well as limiting pocket formation which may increase purge times.

Gas flow for the first gas may generally travel in the direction associated with arrows 128 through upper plate first gas hole 44, into gas cavity 46 and through slots 102 in protrusions 104. Gas flow for the second gas may generally travel in the direction associated with arrows 130 through upper plate second gas hole 42, into channels 50, followed by second gas cavity 52 before exiting between protrusion outer surface 112 and slots 86.)

FIG. 9 illustrates an enlarged view of a portion of showerhead 26 and specifically shows protrusions 104 with slots 102 therein positioned within slots 86 of base plate 36. While the operation and arrangement of the showerhead remains the same, it will be appreciated that slots 102 may extend approximately two-thirds of the distance from top side 98 to protrusion bottom surface 108 at a first radius before a second, smaller, radius is reached in slots 102. A shoulder 132 may mark the transition from the first radius to the second radius, which may be advantageous for gas flow characteristics both during processing and purging operations. In another implementation, shoulder 132 can be flat as shown or angled inwards to assist the flow of gas from 128 into the various slots 102 before contacting angled side wall 134.

FIG. 10 is an even greater magnification of the showerhead. Specifically, shoulder 132 can be seen in greater detail, as well as the various components from the first radius above the shoulder to a smaller radius below shoulder 132. It should be appreciated that the incorporation of shoulder 132 and varying/different radii within slots 102 are merely examples of various configurations which may be utilized and are not intended to in anyway limit the disclosure. Protrusions 104 may include an angled side wall 134 to provide an even flow of the gas from slot 102 as it exits the protrusion. As can also be seen, a gap is formed between protrusion outer surface 112 and slots 86 which is used to convey the second gas into the reaction chamber. In one implementation, the gap G between protrusion outer surface 112 and slots 86 is between 0.575 mm and 0.800 mm, while the gap S in slots 102 is between 0.636 mm and 1.100 mm. In another implementation, the gap G may vary between 0.100 mm and 2 mm and the gap S may vary between 0.100 mm and 2 mm. In still another implementation, the gaps G and S may vary from radial positions such that gaps G and S increase or decrease from radially inward to radially outward positions or from radially outward to radially inward positions.

FIGS. 11 and 12 illustrate enlarged bottom views of the assembled showerhead 26 showing the gaps G and S. Further, arrows 136 illustrate the directional movement of gas flow after exiting gaps G and S. Specifically, both gases flow radially outward after passing protrusion bottom surface 108. Advantageously, the plurality of overlapping rows of slots 86 and 102 provide a uniform stream of gas in a generally radial direction. The overlapping nature helps to assure that terminating areas 138 of a particular slot 86 and 102 still see gas from the radially inward adjacent row. Accordingly, a more uniform gas flow is achieved since there is overlap at each terminating area 138.

FIG. 13 illustrates a second aspect showerhead 140 having components generally similar to showerhead 26. Upper plate 32 includes secondary gas lines 142 extending from gas cavity surface 122 through top side 114. In one implementation, there may be six or more secondary gas lines 142 positioned near the periphery of gas cavity surface 122, although any number of secondary gas lines 142 may be utilized, including without limitation, 1, 2, 3, 4, 5, or more than 6. Secondary gas lines 142 may feed by a plenum 144 or a plurality of single plenums at each secondary gas line 142, where an inner o-ring 146 and an outer o-ring 147 are used to seal a cap 148. A valve 150 is positioned on cap 148 and may be extend through cap 148. A hole 149 may be located within cap 148 to allow valve 150 to communicate with plenum 144. A valve gas line 152 is also connected to valve 152 and in fluid communication with plenum 144 through valve 150. While only a single valve 150 is shown for plenum 144, any suitable number of valves may be utilized, and in one implementation there are as many valves as there as secondary gas lines 142.

A plurality of secondary gas lines 154 may be included in base plate 36 which are in fluid communication with a plenum 156 or a plurality of plenums as applicable. An inner o-ring 151 and an outer o-ring 153 may once again seal plenum 156 and caps 148 together while a valve or valves 150 are positioned on caps 148. A hole 155 may be positioned in cap 148 so that valve 150 can communicate with plenum 156. Still further, valve gas lines 152 are once again connected to all valves 150 in this implementation. Similar to the valves for upper plate 32, valves in base plate 36 may also be any suitable number, the number of plenums may vary, and the number of secondary gas lines may vary without departing from the spirit and scope of the disclosure.

In operation, valves 150 operate to provide a positive pressure to flow a carrier gas during purging steps or a negative pressure to withdraw gas from the showerhead gas cavities (46 and 52) respectively. For example, in one implementation, valves 150 of upper plate 32 may provide a purge gas flow of carrier gas, while valves 150 of base plate 36 may provide a vacuum to remove unused precursor remaining within the showerhead second gas cavity. In the same manner, the roles may be reversed so that valves 150 of upper plate 32 provide a vacuum, while valves 150 of base plate 36 provide a purge gas. In still another implementation, valves 150 may provide a purge gas flow in both the upper plate 32 and the base plate 36 or valves 150 may provide a vacuum in both the upper plate 32 and the base plate 36. A person of ordinary skill in the art will immediately appreciate that a number of operations may be utilized from the same valve configurations without departing from the spirit and scope of the disclosure. It may also be that the vacuum or purge is pulsed during different steps, for example, in an ALD process where the valves are open during purge steps to assist in removal of precursor from volumes after precursor(s) pulses.

FIG. 14 illustrates a third aspect showerhead 158 which is similar to showerhead 140 in that both showerheads utilize valves 150 for providing a purge gas or a vacuum as the application may require. Several different features include an inner o-ring 160 and an outer o-ring 161 surrounding an exhaust feed line 163 adjacent cap 148 and a plenum line 162 connecting plenum 156 and valve 150. Specifically, exhaust feed line 163 connects valve 150 and secondary gas line 154 such that imparting a vacuum on valve 150 removes unused precursor in second gas cavity 52 and dumps the unused precursor directly into exhaust channel 72. Valve 150 in upper plate 32 may operate in a similar fashion to provide a vacuum which may or may not lead to exhaust channel 72 or may provide a purge gas of an inert gas to assist with the purging operation. The various arrangements, orientations, modifications, and procedures discussed above for showerhead 140 may be incorporated into showerhead 158 without departing from the spirit and scope of the present disclosure. Accordingly, it is seen that a number of changes may be made to assist with decreasing resonance time and increasing the purge efficiency.

The above described showerhead and gas delivery system may be utilized in a number of processing applications, including chemical vapor deposition (CVD) and Atomic Layer Deposition (ALD) or a combination thereof. One particularly useful application is depositing transition metal carbides, borides, and silicides using transition metal halides and either a metal organic compound or a silicon/boron hydride. Further, positive results can also be obtained by using transition metal halides with a metal organic compound and a silicon or boron hydride. Also nanolaminates of pure metal and metal nitrids or carbides can be deposited. Examples of suitable metal organic compounds include, but are not limited to, trimethylaluminium (TMA), triethylaluminium (TEA), triethylborane (TEB), dimethylaluminum hydride (DMAH), dimethyl ethylamine alane (DMEAA), amine aluminaborane (TMAAB) and related chemistries. Examples of suitable silicon and boron hydrides include, but are not limited to, silylene (SiH₂), disilane (Si₂H₆), trisilane (S₃H₈), diborane (B₂H₆), and related chemistries.

In operation, metal organic compounds tend to more easily decompose in the presence of transition metal halides. Accordingly, it is advantageous to deposit transition metal carbides, which may include silicon or boron elements, through a gas separated showerhead to avoid any residual chlorine in the showerhead causing decomposition of the organic compound well before reaching a wafer surface. Decomposition of this nature can lead to particle formation and increased build-up which may shed film and also create unwanted particles within the chamber.

Advantageously, showerheads 26 may include separated gas cavities 46 and 52 for example, with first gas cavity 46 being distal to the wafer or processing area 74 and therefore being generally cooler than second gas cavity 52 which is located proximate and even adjacent the wafer processing area 74. Further, first gas cavity 46 may include cooling fins 38 which further help to control and/or reduce the temperature within first gas cavity 46 with respect to second gas cavity 52. Even though first gas cavity 46 is in fluid communication with processing area 74, spacing first gas cavity 46 from the processing area allows the precursor within the first gas cavity to be more stable during processing. In this arrangement, it is advantageous to locate metal organic chemistries in the first gas cavity 46 and locate transition metal halides in the second gas cavity 52, thereby positioning the transition metal halide gas cavity between the processing area and the metal organic source cavity in the showerhead 26. Thus, the metal organic sources are positioned further away from the transition metal halide sources when both the metal organic and the transition metal halide sources are within the showerhead 26.

Alternatively, a silicon or boron hydride may replace the transition metal halide in the second gas cavity and operate in a similar fashion to function as an insulator for the metal organic precursor or source in the first gas cavity. Thus, it is advantageous to locate the less thermally stable precursor in a showerhead gas cavity that is distal the processing area, while locating the more thermally stable precursor in a showerhead gas cavity that is proximate the processing area. While the description of various metal organic sources, transition metal halide sources, and silicon/boron hydrides has been demonstrated in showerhead 26, it is suitable to use any gas separated showerhead so long as the sources do not interact with one another until after exiting the showerhead and the relative positions of the sources in the showerhead are utilized.

These and other embodiments for methods and apparatus for a reaction chamber with a showerhead having multiple gas outlets concentrically positioned and having an arcuate shape therein may incorporate concepts, embodiments, and configurations as described with respect to embodiments of apparatus for measuring devices described above. The particular implementations shown and described are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the aspects and implementations in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the system may not be described in detail. Furthermore, any connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or physical couplings between the various elements. Many alternative or additional functional relationship or physical connections may be present in the practical system, and/or may be absent in some embodiments. Further, various aspects and implementations of other designs may be incorporated within the scope of the disclosure.

As used herein, the terms “comprises”, “comprising”, or any variation thereof, are intended to reference a non-exclusive inclusion, such that a process, method, article, composition or apparatus that comprises a list of elements does not include only those elements recited, but may also include other elements not expressly listed or inherent to such process, method, article, composition or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present invention, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles of the same. 

What is claimed is:
 1. A showerhead comprising: a base plate comprising a least a portion of an exhaust channel and having an opening and a plurality of base plate slots; a middle plate positioned within the opening and having a plurality of middle plate slots and protrusions, the protrusions each comprising a protrusion slot; and, an upper plate comprising a top surface having a plurality of cooling fins formed therein, a first gas hole and a second gas hole, wherein the first gas hole conveys a first gas into a first gas cavity and the second gas hole conveys a second gas into a second gas cavity, wherein each of the plurality of base plate slots is concentrically aligned with the plurality of middle plate slots, wherein the first gas cavity is defined between the upper plate and the middle plate and the second gas cavity is defined between the middle plate and the base plate, wherein the first gas cavity and the second gas cavity are fluidly coupled to the exhaust channel, wherein a first gas purge channel extends from the first gas cavity, wherein the first gas purge channel feeds into a first plenum, wherein the first plenum is coupled to a first valve, wherein a second gas purge channel extends from the second gas cavity, wherein the second gas purge channel feeds into a second plenum, wherein the second plenum is coupled to a second valve, wherein one of the first and second valves is configured to provide a purge gas into the first or second gas cavity, wherein the other of the first and second valves is configured to provide a negative pressure to the first or second gas cavity, wherein the first gas purge channel extends from the first gas cavity through an opening that is separate from the first gas hole, wherein the second gas purge channel extends from the second gas cavity through an opening that is separate from the second gas hole, wherein the first and second gas purge channels do not convey the first gas or the second gas into the first and second gas cavities, wherein the first gas cavity is in fluid communication with the first gas hole and the second gas cavity is in fluid communication with the second gas hole, wherein the protrusions extend into the base plate slots, wherein a gap is formed between each protrusion and each base plate slot and the gap is in fluid communication with the second gas cavity, wherein the protrusion slots are in fluid communication with the first gas cavity, wherein the protrusion slots comprise a first radius extending through a portion of the protrusion and a second radius that is smaller than the first radius extending through another portion of the protrusion, wherein the protrusions extend to at least a bottom surface of the base plate slots, and wherein the gap terminates at the bottom surface.
 2. The showerhead of claim 1 wherein the protrusions extend beyond a bottom surface of the base plate slots.
 3. The showerhead of claim 1 wherein the plurality of base plate slots and the plurality of middle-plate slots are oriented in a plurality of rings, wherein adjacent base plate slots are offset with respect to one another.
 4. The showerhead of claim 1 wherein the plurality of base plate slots and the plurality of middle plate slots are oriented in a plurality of rings, wherein base plate slots of every other ring are in alignment.
 5. The showerhead of claim 1 wherein the gap is between 0.575 mm and 0.800 mm.
 6. The showerhead of claim 1 wherein a second gap is formed within each of the plurality of middle plate slots, and wherein the second gap is between 0.636 mm and 1.100 mm.
 7. The showerhead of claim 1 wherein a first gas flows from the first gas cavity formed between the middle plate and the upper plate and a second gas flows from the second gas cavity formed between the base plate and the middle plate.
 8. The showerhead of claim 1 wherein the first valve is configured to provide the negative pressure to the first gas cavity, wherein the first plenum is connected to an exhaust feed line, wherein the exhaust feed line is connected to the exhaust channel, and wherein when the first valve provides the negative pressure, an unused precursor gas in the first gas cavity is moved into the exhaust channel.
 9. The showerhead of claim 1 wherein the first gas purge channel is positioned at a perimeter of the first gas cavity.
 10. The showerhead of claim 1 wherein the first valve is configured to provide the purge gas into the first gas cavity.
 11. The showerhead of claim 1 wherein the first gas purge channel is operatively connected to a vacuum.
 12. The showerhead of claim 11 wherein the first gas purge channel removes the first gas during a purging operation.
 13. The showerhead of claim 1 wherein the second gas valve is configured to provide the negative pressure to the second gas cavity, wherein the second plenum is connected to an exhaust feed line, wherein the exhaust feed line is connected to the exhaust channel, and wherein when the second valve provides the negative pressure, an unused precursor gas in the second gas cavity is moved into the exhaust channel.
 14. The showerhead of claim 1, wherein a plurality of apertures extend from a top surface to a bottom surface of the middle plate and are separate from the plurality of middle plate slots.
 15. The showerhead of claim 14, wherein the plurality of apertures are in fluid communication with the second gas cavity.
 16. The showerhead of claim 1 wherein the plurality of middle plate slots are generally arcuate in shape.
 17. The showerhead of claim 16 wherein each of the plurality of middle plate slots extend less than 50 percent of a circular distance of the showerhead body.
 18. The showerhead of claim 1 wherein a gas in the base plate slots does not contact a gas in the middle plate slots until both of the gasses have traveled completely through the base plate slots and the middle plate slots.
 19. The showerhead of claim 1, wherein each of the protrusion slots further comprises an angled sidewall extending from the second radius. 